Can Self-Swabs Make HIV Exposure and Risk Reporting More Accurate?

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A new study conducted in South Africa finds that when cisgender women are given the tools to assess their HIV exposure risk at home, those tools can yield far more accurate results than a sit-down interview with an HIV clinician.

The study also pioneered a new use case for swabbing kits, yielding valuable insights that lead author Maria Lemos, Ph.D., says may one day lead to a new method of self-testing for HIV exposure at home. Research was led by the HIV Vaccine Trials Network (HVTN), headquartered at the Fred Hutchinson Cancer Research Center (Fred Hutch) in Seattle.

The study, which was published June 1 in the Journal of Acquired Immune Deficiency Syndrome, was born out of a need to give women more autonomy when it comes to their HIV exposure -- particularly because some women are unable to negotiate condom use during sex, said Lemos, a Fred Hutch staff scientist.

Condomless sex is a major risk factor for young women, with HIV now ranking as the leading cause of death globally among women of reproductive age. "We want to give them a tool to say, 'If I don't have control over whether a condom is used, is there something else I can do?'" said Lemos.

All told, the study demonstrated that women are capable of using a self-swabbing kit correctly, and the kit itself was able to determine when women had unprotected sex. However, the kit was not as successful at identifying HIV exposure, indicating that it would need to be refined before being used broadly for this purpose.

"This is a proof-of-concept study showing that HIV exposure can be detected by vaginal swab in young, sexually active cis women engaging in receptive sex with male partners," said Oni Blackstock, M.D., M.H.S., assistant commissioner for the Bureau of HIV/AIDS Prevention and Control for the New York City Health Department, who was not involved in the study.

"The study findings also indicate that vaginal swabbing is feasible and acceptable for women," Blackstock said, but she cautioned that "more study is likely needed to understand the low rates of HIV exposures detected as compared to what was expected."

Daily Reporting of Sexual Activity via a Mobile App and Self-Swabbing

Researchers leading the HVTN study had three main objectives. The first was to see if women would be more likely to report unprotected sex accurately on a mobile app than when visiting a clinic for a face-to-face meeting.

The idea, said Lemos, is that women "might be more comfortable [responding] in an app in a little phone, because then you won't have the problem of the participant accommodating the answer to please the interviewer."

The second objective was to see if daily reporting of sexual activity (via the app) would be more accurate than reporting sexual activity once per week in a clinic setting.

"We wanted to know … whether asking those questions daily would change how precise those answers are," she said.

The third objective had to do with the daily self-swabbing kits, which are made by the U.S.-based company Hologic and sold as the Gen-Probe Aptima Swab Kit.

Typically, these kits are used for sexually transmitted infection (STI) detection, but Lemos explained that kits were co-opted in this study and used to detect glycogen (a byproduct of the vaginal microbiome), Y-chromosome (to detect semen), and HIV RNA.

After obtaining approval from an ethics board, the researchers recruited 50 HIV-negative cisgender women ages 18 to 25 in Soweto, South Africa. The women were sexually active and considered at high risk for HIV. At the start of the study, all women were given HIV prevention counseling and were trained on how to use the mobile phone and how to collect a vaginal swab.

Every day for three months, the women collected vaginal samples -- a process that involves placing a swab that looks like a long Q-tip in the vagina for 10 to 30 seconds and placing that swab into a tube filled with solution. The samples did not need to be refrigerated. Women also reported their sexual behavior using the mobile app and visited a local clinic for in-person evaluations and other testing.

The first objective of the study -- mobile app reporting -- found that women were able to accurately report sexual activity via the mobile app. Among women who reported abstinence or protected sex for the three days prior, only 5% (10/187) of swab samples had detectable Y-chromosome, indicating the presence of semen (and therefore, likely unprotected sex). Meanwhile, among women who reported unprotected sex on the mobile phone, just over half (51%) of swab samples had Y-chromosome.

These figures are striking in comparison to the inaccuracy of face-to-face sexual health visits, in which women may not remember sexual activity that took place several days prior or may omit information in the face of stigma -- real or perceived -- about certain sexual behavior, including how often they have sex or how many partners they have had.

"We know that patients often feel a great deal of judgement from providers and can be made to feel uncomfortable during sexual history taking," said Blackstock. "Reporting via mobile app may reduce the likelihood of women providing socially desirable responses, because they are interfacing with an app as opposed to a clinician."

The third objective of the study -- women's ability to self-swab correctly -- was a resounding success. Overall, 94% of the swabs conducted by the women at home were performed correctly, as indicated by the presence of glycogen. If the women had swabbed the labia, rectum, or some other surface of the body, glycogen would not have been present. This success rate is on par with the success rate of trained clinicians, explained Lemos.

"They were finding ways to do this every day, and some of the women in the study don't even have access to a private bathroom," said Lemos. "That really says [that] self-swabbing is something women can do."

HIV Exposure Was Largely Undetected or Absent

In addition to understanding whether women could use the product correctly, and if it could reliably indicate unprotected sex, researchers were also interested in using the self-swabbing kit to detect whether or not a woman had been exposed to HIV during sex. This portion of the study did not pan out as anticipated. Surprisingly, although the women were known to have high-risk sex, the test only detected two HIV exposures -- both from the same woman, and both from samples she collected within an hour of intercourse.

None of the women seroconverted during the study. It's possible that HIV exposures were few because women who participated in the study were able to decrease their risk behavior, said Lemos. But it's also possible that the swabbing kit and assay technology was not powerful enough to detect the majority of HIV exposures.

HIV RNA tends to degrade quickly in the vaginal environment, potentially making it more difficult to detect HIV exposure if swabbing took place more than an hour after intercourse, Lemos explained.

"So far, no one had been able to detect an HIV exposure in the vagina" using this technology, said Lemos. "Our results show that it is possible," she said. However, "for real, practical reasons, we want to have a test that could allow us to detect HIV for a little bit longer" after exposure.

Could Self-Swab Tests Be the Future for Everyone?

Lemos is also leading a follow-up study with a similar design among men who have sex with men in the United States to explore the self-swabbing technology's potential for rectal HIV exposure detection.

Eventually, the self-swabbing technology could make it possible for women to test for HIV exposure from the privacy of home, although Blackstock questioned the utility of such an intervention.

"In the future, this could potentially be a technology that women use to assess their HIV risk, although just given the sexual behaviors women reported and community HIV prevalence, they would already be at high risk for HIV," Blackstock said. "So, it is not immediately clear what this would add in a real-world setting. This may be a tool more useful for research studies."

"We want to be able to offer that opportunity to women who want more control over their sex lives," said Lemos. "We're working on it, but we're not there yet."